Aquatic propulsion by means of oscillating fins

ABSTRACT

The aquatic propulsion proposed uses oscillating blades provided with independent, mutually parallel vertical shafts affixed, at the upper end thereof, to a single horizontal oar of planar profile. The blades or fins being of different length on the basis of the distance between the fastening point of the actual oscillation shaft thereof and the shaft on which the oar rocks. Propulsion is achieved when the user applies a force in traction or thrust on any of the two grips provided at either end of the handlebars, or in opposite directions on both at one and the same time. The movement is transmitted to the rotary shaft and then to the profile section on which the fins are arranged, which causes the fins to move transversely and alternately in both directions, causing displacement of the water and the propulsion of the swimmer or floating object or vehicle, in the intended direction.

TECHNICAL FIELD

The invention relates to high-performance aquatic propulsion means usingoscillating fins, intended specifically to propel small aquatic vehiclesand floating surface objects, although it may also be used as underwaterpropulsion for divers and submarines.

PURPOSE OF THE INVENTION

As suggested by the title of the present description, the subject matterof the invention is aquatic propulsion means that use oscillating bladesor fins transverse to the direction of travel to propel a floatingobject or vehicle, the novel features of which substantially reduce thestroke length of the surface of the blade at a neutral or negativeangle, resulting in fewer oscillations about the longitudinal axistransverse to the waterline because they enable the propelling elementto be as close as possible to the parallel lower plane of the vehicle,and for the axis of rotation of the oscillating arm or oar to be locatedin front of the keels of the axis of maneuver, improving the actualhydrodynamic coefficient and obtaining a propulsion efficiency that ismuch greater than had been achieved with these systems. Moreover, itallows the speed to be varied at frequencies of actuation and identicaltransverse strokes, and it makes it easy to swap the fins in seconds,including in the water, if they are damaged by impact or to replace themfor others that enable the propulsion element to be adapted to theenvironment in which the vehicle is moving, either to obtain greaterpropulsion capacity, or with softer edges to be used in the presence ofbathers.

Another purpose of the invention is to provide simple, powerful andhighly maneuverable muscular propulsion that is suitable for use bychildren, old people and people with disabilities.

BACKGROUND TO THE INVENTION

The most powerful and simple known system for muscular propulsion inwater is unquestionably the use of oscillating fins, used by thousandsof species of fish and marine animals in all seas, rivers and lakes inthe world, with the fastest reaching speeds exceeding 100 km/h. However,to date human beings have been unable to achieve even barely acceptablepropulsion coefficients using alternating oscillating devices fittedwith submerged fins, which may be partially flexible or rigid and shapedvertically or horizontally in relation to the vehicle.

A conventional oar with a stroke perpendicular to the longitudinalwaterline can only achieve propulsion in one direction, which involvesan unnecessary loss as it moves out of the water to return to theinitial position. The propulsion achieved varies proportionally as afunction of the angle, but always within positive parameters, with entryclose to the stern at a minimum propulsion angle, travel towards theright angle where propulsion is neutral, before reducing again whenmoving towards the bow. The loss of energy is greater the closer the oargets to the direction of travel, on account of which increasingly largeoars are used to provide a greater stroke length close to neutral.

Unlike the conventional oar, propulsion using oscillating blades or finswith a stroke transverse to the direction of travel achieves maximumpropulsion at the beginning of the stroke, reducing proportionatelyuntil the right angle, or parallel to the direction of travel, and inthis exact position the direction of the water is transverse to theforward movement, which is useless for propelling us, but from thispoint it becomes negative, which brakes us.

The known prior art has attempted to address this problem by providingthe oscillating device with a fin provided with an independent shaftconcentric to the shaft of the mechanism of the oscillating oar or arm,and stops limiting the stroke of the fin, which enables it to oscillatein a direction opposite the direction of the profile until it reachesthe stop position and from this point to acquire the same direction, atan angle opposite the profile, which is the propulsion position.However, the “accompanying” movement with no propulsion capacity untilthe stops are reached involves wasting a large percentage of the totalstroke.

If, for example, in an oscillating oar 100 cm long, the fin represents50% of the total, and both oscillate at angles of 90°, the“accompanying” stroke performed by the fin to reach the propulsionposition between both limit stops represents practically 50% of thetotal, with no propulsion capacity. Furthermore, it requires the angleof actuation to be kept constant, because the angle of the fin remainswith an invariable stroke of 90°, which means that each degree that wereduce increases the “accompanying percentage”, but what usually happensis that, when attempting to increase the speed of the vehicle, the userincreases the actuating rhythm, usually reducing the angleproportionately, on account of which the increased frequency in factreduces the propulsion capacity. Many attempts have been made toincrease propulsion without resolving the problem, reducing the anglebetween the stops and increasing the proportional length of the blade,which increases the accompanying stroke by the same proportion, as wellas reducing the positive stroke to the line parallel with the directionof travel entering before the negative angle. On account of this, therehave been many attempts to try to use fins with a rigid frame and aflexible part in the central surface, with very poor results.Consequently, in practice, there are no known aquatic vehicles that arecurrently propelled using oscillating mechanisms of this type.

In ordinary propulsion using an oscillating fin or blade positionedvertically and moving transversely to the direction of travel, theoscillating shaft of the mechanism is located to the stern, behind thekeel of the vehicle, which causes significant oscillations in course,contrary to the stroke of the blade in both directions of actuation,significantly worsening the actual hydrodynamic coefficient. In otherversions with fins positioned horizontally, the undulating effect iscaused on the longitudinal waterline, which has the same negativehydrodynamic effect.

The use of a fin oscillating across the direction of travel andpositioned in front of a central keel arranged to the stern is known,which coincides with the fin at an angle very close to the line parallelto the direction of travel, however small it is on both sides of thestroke, which results in a significant loss of propulsion in thepositive propulsion zone, without resolving the “accompanying”percentage and although the impact on the course is less than if the finwere oscillating behind the keel, it causes constant oscillations in thetransverse waterline, on account of which it is not very stable inaddition to providing substandard propulsion. There are also no knownpractical applications of this system at this time.

It improves the prior art in the propulsion using oscillating fins,reflected in propulsion essentially for diving, where the fins areattached to the sole of the diver's foot, in the same plane (at an angleof 90° to the leg) by means of footwear or similar, which extends fromthe end of the foot in two parallel straight profiles, which may berigid or semi-rigid, between which the central body of the fin isdivided into a plurality of oscillating segments transversal thereto,but in the same plane and of similar length, provided with independentshafts that are linked to the extremities thereof with each one of bothprofiles, such that the position of each segment in relation to thedistance to the hip or knee joint (depending on whether the user movesthe fins with straight legs and the instep of the foot extended to themaximum, or bent legs, where the length of the fins when idle isparallel to the swimmer, but shifted by a distance equal to the distancebetween the sole and the knee) and the corresponding axis thereof, isdifferent, meaning that the accompanying stroke and the point ofnegative-angle entry are also different, which represents an enormoushydrodynamic problem to determine the optimum stroke to minimize theaccompanying percentage or the entry into negative propulsion, which isdifferent for each of the segments of the fin, which makes them verycomplicated to use, even more so bearing in mind that the swimmer ordiver has to coordinate the stroke of both fins and the position of theinstep simultaneously, which is very complicated, on account of whichthis type of fin has not replaced conventional fins.

According to the novel features of the present invention, the improvedaquatic propulsion using oscillating fins is designed to make optimumuse of the muscle energy used—which is finite—thereby substantiallyimproving the efficiency of the oscillating fins of the propulsionelement, also incorporating a suitable positioning of the elements ofthe mechanism and of the user, whose weight in small floating structuresrepresents a significant percentage of the total mass, which has asignificant impact on stability. For this purpose, the handlebars thatactuate the oscillating mechanism, the axis of rotation thereof, the oarand the oscillating fins, in this order, as well as at least 50% of theuser's mass are located centrally in relation to the transverse line ofthe vehicle, and in front of the keels of the axis of maneuver. Toensure that the oscillating movement of the fins during forward movementoccurs very close to the keels located to the stern, in parallel and asfar away as possible from the longitudinal center of the vehicle, giventhat a central keel is a destabilizing hydrodynamic obstacle, much moreso than if there are two, and they are located on both sides, becauseeven with oar opening angles greater than 50°, from 0° in bothdirections the maximum position of the blades is very close to the rightangle or neutral, on account of which the water is propelled in adirection very close to the line parallel to the corresponding keel inboth directions of the start of the stroke, with a high propulsionratio, however towards the end of the stroke, the direction of the waterchanges towards the approaching keel, tending to balance the vehicle,instead of destabilizing it. With angles below 30° in both directions, alarge percentage of the flow moved flows between the two keels, with noparticular impact on the transverse or longitudinal waterline. However,since the length of the blades or fins is proportional and increases,the further away they are from the axis of rotation of the oar, the oneswith a larger surface area and longer stroke are therefore the ones thatmove the greatest quantity of water and that are closest to the keels,on account of which the oscillating effect on the course is minimal,which would not be the case if the fins were to move behind the keels.Equally, the eccentric position of the blades in relation to the lowerface of the oar, according to claim 5 of this report, enables this to beas close as possible in parallel to the structure of the vehicle, havinga minimum impact on the center of gravity during forward movement,however, by lowering it during turning maneuvers, when moving thepropulsion element from the central axis of the vehicle at a low depthin relation to the waterline, propelling it against the centrifugalforce.

According to the aforementioned features, the handlebars and thereforethe oar can rotate through 360° and the oscillating action can beperformed in any position. The course is determined at all times by theintermediate point of the oscillating stroke.

There are no known propulsion methods such as the one proposed in thepresent invention, in which the corresponding oscillating fins haveindependent oscillating shafts that are eccentric in relation to thelower plane of a single profile or oscillating flattened straight oar.

Furthermore, there are no known propulsion methods incorporatingoscillating fins arranged vertically in the same plane, of similarheight, but in which the length of each fin is different, proportionallyincreasing in relation to the previous one as they move away from theaxis of rotation of the oar in relation to the shaft thereof,consistently with the greater or lesser stroke of the oar in relation toeach point of the length thereof, which guarantees the synchrony of allof the blades during the “accompanying” stroke between the respectivelimiting stops thereof.

Furthermore, there are no known mechanisms for limiting the oscillatingstroke of the fins such as the one described in the present invention,which makes it possible to position all of the blades or fins at thesame angle, and simultaneously to vary it at will at any time,regardless of the oscillating stroke of the oar, using an operatingmechanism located at an accessible point of the handlebars, which makesit possible to determine, even for a child, the maximum angle reached bythe fins in each direction, and in which position the operating handlerelated to same should be positioned to obtain the maximum propulsioncapacity. Furthermore, said mechanism is totally unrelated to anystructure that is not a direct part of the propulsion system, such thatthe actuating handlebars can be rotated in any direction withoutlimitation and without altering the position determined in advance forthe fins.

DESCRIPTION OF THE INVENTION

The invention relates to a set of steering handlebars with anoscillating action comprising a cylindrical profile (14) transverse tothe direction of travel when in idle position, provided at theextremities thereof with as many levers or handles (16) and a centralvertical prolongation (13) having a hollow square profile and intendedto consistently and gaplessly connect with the square segment (12 b) ofthe upper end of the cylindrical rotary shaft (12 a) of the oscillatingmechanism, which contains a cylindrical opening (48) that runs throughthe entire length thereof. At the bottom end, the shaft (12 a) isattached at an angle of 90° to the round end of the oar (11) whichextends in a straight flattened profile transverse to the handlebars(14) and, at the opposite end, the oscillating shafts (9) of the blades(1, 2, 3, 4, 5) passed through the profile of the oar (11) from theupper plane and are attached to the plane, for which there is a largerectangular flattened head (27) and as many threaded holes (28) arrangedequidistantly on both sides of the shaft (9) which are used to connectthe conical head screws (49) passing through the profile (11) from thelower plane through the apertures (47) of conical profile provided tocenter and attach the shafts (9) to the oar (11), although the diameterof the hole (46) of profile similar to the screw is larger than theshaft. From this point, they extend in a straight and eccentric fashionin relation to the lower plane to the opposite end where, preceded by aconical point (10) they have as many peripheral slots (45), said shafts(9) being inserted into the respective apertures (51) thereof providedin one of the vertical edges of each fin (1, 2, 3, 4, 5), and when theconical end (10) of the shaft (9) meets the aperture of the slottedelastic segment (8), the diameter of which is less than the diameter ofthe shaft (9), it expands enabling it to pass through and subsequentlyis seated in said slot (45) such that it is perfectly attached but canbe easily released by inserting a flat element into the slot of thesegment (8) and rotating it slightly, which forces it to expand andenables it to be disconnected.

In parallel and in contact with the lower plane of the oar (11) there isa straight, flat plate (6) of similar width that has as many slots (32)as there are shafts (9) attached to the oar (11), which are provided toenable the movement of the plate (6) but also to limit it to the lengthof said slots, as they pass through said slots. On the same lower planeof said plate (6) are attached the stops (7), which are arranged inpairs and equidistantly on either side of each of the slots (32), andtherefore of each of the parallel and eccentric shafts (9), in relationto a single flat oar (11), distributed longitudinally at a graduallyincreasing distance equivalent to the length of each of the fins (1, 2,3, 4, 5) progressively from the shortest (1) that is closest to the axisof rotation of the oar, to the longest (5), which is placed at thedistal end.

According to the invention, the oscillating stroke of the set of blades(1, 2, 3, 4, 5)—shown in the drawings as a set of five purely by way ofexample, but that could be a set of any number, provided the principleof proportional length is observed—is limited by as many stops (7) oneach side, which are attached to the common flat plate (6), which canmove forwards or backwards, and consequently so can the stops (7),enabling the maximum limit of the oscillating stroke of the blades (1,2, 3, 4, 5) to be modified at will regardless of the oscillating strokeof the oar (11). Said plate (6) has an attachment element (43) at theend thereof closest to the rotary shaft (12 a) of the oar (11) thatconnects to the aperture (44) formed in the end of a piston (33) thatruns through a guide element (26) to an articulated shaft (41) sharedwith the end of a connecting rod (34) that extends and connects to ashaft (40) seated in the end of the eccentric plate (35) attached to thecentral rotary shaft (21) of the articulated mechanism. Said shaft (21)passes from this point through the hollow inside (48) of the rotaryshaft of the oar (12 a) to the opposite end thereof, where there is aperiphery slot (36) provided to seat the corresponding elastic ring (37)that determines the position thereof on the shaft (12 a), but thatenables it to rotate independently thereof, extending from this point,once the vertical square profile (13) attached to the handlebars (14)has been connected to the square segment (12 b) until it passes abovethe aperture (42), centered vertically on the aperture (48) in a semicircular plate (15) attached to the center of the handlebars (14). Onthe plane of said plate (15) there is a plurality of radial slots (17)equidistant from the aperture (42) and the shaft (21), the end of whichis threaded (39) and has as many opposing planes (38) matching thestructure of the hole (29) of the supporting element (18) provided alongwith the nut (22) as attachment elements to the shaft (21). At theopposite end, there is a vertical slot that houses the operating handle(19) that oscillates about a transverse shaft (25) that passes throughthe rotary supporting element (18) and said handle (19), the lower edgeof which acts as a ratchet and passes the lower plane only when the endof the handle is parallel to the upper plane of the supporting elementand is opposite the radial slots (17), forced at the inclined edgethereof by an elastic element (20) attached to the supporting element(18) when inserted into the slot (17) chosen by the user to determinethe position at which the handle (19) is released, determining therebythe position of the plate (6) and the stops (7) in relation to theshafts (9) that limit the angle and the oscillating stroke of the blades(1, 2, 3, 4, 5), on account of which it can be adjusted, on the basis ofthe maximum angle reached in the alternating stroke of the handlebars(14) to obtain the maximum desired acceleration, without entering thenegative angle.

Propulsion is generated when the user applies muscle force, traction orthrust, to either of the two handles (16) provided at each end of thehandlebars (14), or in opposite directions on both simultaneously, saidmovement being transmitted to the rotary shaft (12 a) and then to theprofile (11) on which the fins (1, 2, 3, 4, 5) are arranged, forcingthem to move transversely and alternately in both directions, therebymoving the water and propelling the floating vehicle, object or swimmerin the desired direction, which corresponds to the midpoint of theoscillating stroke of the oar (11).

It should be noted that none of the elements that make up the structureof the propulsion system has any prior limitations that prevents it fromrotating through 360°, on account of which the alternating oscillatingmovement can be applied at any time. The position in which thehandlebars (14) are placed before being actuated enables the structureto move forwards or backwards or to turn in any direction.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In a preferred embodiment of the invention, the actuating handlebars,rotary shaft, oar and fins, in this order, as well as at least 50% ofthe user's mass are located on the center of the direction of travel, infront of the axis of maneuver formed by the two keels (53) located atthe stern and as far away from one another as possible on either side ofthe floating object or vehicle in which the propulsion device isinstalled, but nonetheless locating the rotary shaft of the oar asclosely as possible, such that the fin at the opposite end passes closeto the keels, such that actuating the propulsion element causes minimumoscillations to the course and also reduces the turning circle of thevehicle, affording it extraordinary maneuverability.

A preferred embodiment of the invention includes the use of severaloscillating fins with independent parallel shafts eccentric in relationto the lower plane of the single flattened oscillating profile, thewidths of which vary in proportion to the distance between thecorresponding shaft thereof and the rotary shaft of the oar, where theoscillating stroke of each of the blades is limited in both directionsby stops attached to a common plate, the position of which may be variedat will in relation to all of the blades of the propulsion system at thesame time, increasing or reducing the maximum angle, regardless of theangle of the oar, which makes it possible to choose the angle mostsuitable to the speed of movement at any time.

Equally, the use of shafts attached to a single straight profile and therapid attachment system for the oscillating fins enable them to beswapped rapidly, retaining the length corresponding to the positionthereof, whether they are taller or shorter, and even changing thenumber of fins to obtain the maximum possible propulsion power, in anyenvironment and with any floating object or vehicle to which thepropulsion system according to the present invention is applied.

DESCRIPTION OF THE FIGURES

The drawings included in this report are merely an example to assistcomprehension of the invention, and are not limiting.

FIG. 1 shows the actuating mechanism with the propulsion systemattached.

FIG. 2 shows the semicircular base and the radial slots, which arerelated to the ratchet mechanism.

FIG. 3 shows the components of the ratchet mechanism, supportingelement, handle/ratchet and elastic element pressing against the handle.

FIG. 4 shows the articulated mechanism mounted on the rotary shaft andattachment means, and the means related to the plate that enable theangle of the blades to be adjusted and a cross-section of the limitingstops.

FIG. 5 shows the articulated mechanism of the changer.

FIG. 6 is a worm's eye view showing the oar and the blades positioned infront of the keels.

FIG. 7 shows the structure of the blades and the elastic segment toattach it to the shaft.

FIG. 8 shows a blade and the attachment profile of the shaft in twosegments.

FIG. 9 shows the profile of the rotary shaft, the profile of the oar andthe structure of the shafts, as well as the elements enabling them to beattached to the oar and to the blades.

1. Improved means for aquatic propulsion with high-performanceoscillating fins that include means for reducing the negative-anglestroke length of an oscillating fin transverse to the direction oftravel, characterized in that the oscillating fins (1, 2, 3, 4, 5), asshown in FIGS. 1 and 7 of the present description, of which there arefive although there could be a different number, form a rigid propulsionmember comprising segments of similar height but of different lengthsarranged in the same longitudinal plane and fitted with independentoscillating shafts (9) that are parallel to one another, in which thegreater or lesser length thereof depends on the distance between theoscillating shaft (9) thereof and the rotary shaft (12 a) of the oar(11), equivalent to the diametric stroke of the oar (11) in relation toeach point of attachment of the corresponding shaft (9) thereof, thedecreasing percentage being determined by the furthest separatingdistance, for example: if it is 10%, all of the fins will have a lengthequivalent to 10% of the distance between the shaft thereof and therotary shaft of the oar, and so on.
 2. The improved means for aquaticpropulsion with high-performance oscillating fins as claimed in claim 1,characterized in that the oscillating alternating stroke of the fins (1,2, 3, 4, 5) is limited in both directions by as many stops (7) arrangedequidistantly on each side of the axis of oscillation thereof andattached to a straight flat movable plate (6) arranged in parallel andin contact with the lower plane of the oar (11), of similar width,between this and the blades (1, 2, 3, 4, 5), the longitudinal center ofwhich includes a series of as many slots (32) as there are shafts (9)attached to the oar (11) that are provided to enable the plate (6) tomove but also to limit said movement to the length of the slots, as theypass through said slots, the stops (7) being attached in the same lowerplane of said plate (6), said stops limiting the stroke of the bladesand being arranged in pairs and equidistantly on either side of each ofthe slots (32), and therefore each of the shafts (9), on account ofwhich the movement of the plate (6) in either direction changes themaximum oscillating stroke thereof.
 3. The improved means for aquaticpropulsion with high-performance oscillating fins as claimed in claim 2,characterized in that said plate (6) has an attachment element (43) atthe end thereof closest to the rotary shaft (12 a) of the oar (11),which connects with the aperture (44) in the end with a piston (33) thatruns through a guide element (26) to an articulated shaft (41) sharedwith the end of a connecting rod (34) that extends and connects with asecond shaft (40) arranged at the end of an eccentric plate (35)attached to the central rotary shaft (21) of the articulated mechanism,said shaft (21) running from this point through the hollow inside (48)of the rotary shaft of the oar (12 a) to the opposite end thereof, wherethere is a peripheral slot (36) designed to receive the correspondingelastic ring (37) that determines the position thereof on the rotaryshaft (12 a), but that enables it to rotate independently thereof,extending from this point, once the vertical square profile (13) of thehandlebars (14) has been connected to the square segment (12 b) of theshaft (12 a) until it passes above the aperture (42), centeredvertically on the aperture (48) in a semi circular plate (15) attachedto the center of the handlebars (14), on the plane of said plate (15)there being a plurality of radial slots (17) equidistant from theaperture (42) and the shaft (21), the end of which is threaded (39) andhas as many opposing planes (38) matching the structure of the hole (29)of the supporting element (18) provided along with the nut (22) asattachment elements to the shaft (21), and at the opposite end, therebeing a vertical slot that houses the operating handle (19) thatoscillates about a transverse shaft (25) that passes through the rotarysupporting element (18) and said handle (19), the lower edge of whichacts as a ratchet and passes the lower plane only when the end of thehandle is parallel to the upper plane of the supporting element and isopposite the radial slots (17), forced at the inclined edge thereof byan elastic element (20) attached to the supporting element (18) wheninserted into the slot (17) chosen by the user to determine the positionat which the handle (19) is released, determining thereby the positionof the plate (6) and the stops (7) in relation to the shafts (9) thatlimit the angle and the oscillating stroke of the blades (1, 2, 3, 4,5), on account of which it can be adjusted, on the basis of the maximumangle reached in the alternating stroke of the handlebars (14) to obtainthe maximum desired propulsion, without entering the negative angle. 4.The improved means for aquatic propulsion with high-performanceoscillating fins, characterized in that the handlebars (14), rotaryshaft (12), oar (11) and fins (1, 2, 3, 4, 5), in this order, arelocated in front of the two keels (53) located at the stern and as faraway from one another as possible on either side of the floating objector vehicle in which the propulsion device is installed, but nonethelesslocating the rotary shaft of the oar as closely as possible, such thatthe fin at the opposite end passes close to the keels, such thatactuating the propulsion element causes minimum oscillations to thecourse and also reduces the turning circle of the vehicle.
 5. Theimproved means for aquatic propulsion with high-performance oscillatingfins as claimed in claims 1 and 2, characterized in that the verticalshafts (9) on which the fins (1, 2, 3, 4, 5) oscillate are attached onlyby the upper end thereof to a single flat profile, comprising theoscillating oar of the propulsion device (11), extending in a straightbut eccentric manner in relation thereto, such as to bring the oar asclose as possible and parallel to the sliding surface of the vehicle orfloating object.
 6. The improved means for aquatic propulsion withhigh-performance oscillating fins, characterized in that the shafts (9)on which the propulsion blades or fins (1, 2, 3, 4, 5) oscillate thatpass through the flat profile of the oar (11) from the upper plane, havea large rectangular flattened head (27) and as many threaded attachmentholes (28) arranged equidistantly on both sides of the shaft (9) thatare connected with the conical head screws (49) passing through theprofile (11) from the lower plane through the conical apertures (47)provided to center and attach the shafts (9) on the oar (11), althoughthe diameter of the hole (46) through which the shaft (9) passes islarger than the shaft, this feature enabling damaged shafts (9) to bereplaced, even if they receive sudden impacts in shallow environmentsthat could otherwise render the propulsion device unusable.
 7. Theimproved means for aquatic propulsion with high-performance oscillatingfins as claimed in claims 1, 2 and 6, characterized in that said shafts(9) have a peripheral slot (45) at the lower end thereof preceded by aconical point (10) provided so that when the shaft (9) is inserted intothe aperture (51) of the fin (1, 2, 3, 4, 5), when it meets the apertureof the slotted elastic segment (8) of the fin (1, 2, 3, 4, 5), thediameter of which is less than the diameter of the shaft (9), itexpands, enabling the passage thereof and it is subsequently seated insaid slot (45) so that it is perfectly attached, but can be changedeasily by inserting a flat element into the slot of the segment (8) androtating it slightly so that it expands and enables the disconnectionthereof, and furthermore the expandable segment (8) may be omitted andreplaced by the corresponding elastic ring of the type available on themarket, or using shafts (9) with threaded ends, that are attached to thefin at the appropriate position by means of a lock nut, any of thesystems mentioned enabling the rapid disconnection to enable the shaftsor fins to be swapped.
 8. The improved means for aquatic propulsion withhigh-performance oscillating fins as claimed in claim 6, characterizedin that the set of oscillating blades (1, 2, 3, 4, 5) are configuredwith different lengths depending on the distance between the shaft (9)thereof and the rotary shaft of the oar (12 a), although the heightthereof may be similar; the body of the fin (1, 2, 3, 4, 5) is made of aplate of rigid or semi-rigid material having a rounded profile (50) onone of the vertical edges thereof that extends partially in relation tothe total height, the center of which is perforated (51) to receive theshaft (9), of slightly lesser diameter, on which it oscillates; therounded profile (50) may be partially sectioned and split into twosegments (23, 24) of specific height at the ends, also perforated, thatreduce the total thickness of the body of the fin (1, 2, 3, 4, 5),improving the hydrodynamic coefficient thereof; from the lower end ofthe rounded profile (50), the body of the fin has an elastic segment ofthe same profile (8), the center of which is perforated at a diameterless than the diameter of the oscillating shaft (9) and has a diametricvertical slot (52) in the same plane as the body of the fin (1, 2, 3, 4,5), which enables it to expand by inserting the conical point of theoscillating shaft and seating it ultimately in the peripheral slots (45)provided for this purpose in the shaft (9) such that it is perfectlyattached, the disconnection of both being easily achieved by inserting aflat element into the slot of the expandable segment (8) thatfacilitates disconnection when rotated slightly.